The research described in this thesis reports on a 10-month quantitative/qualitative classroom-based study, carried out at a Japanese university, investigating the potential of authentic materials to develop learners’ communicative competence. It was hypothesised that the ‘richer’ input provided by authentic materials, combined with appropriate awareness-raising activities, would be better able to develop a range of communicative competencies in learners (linguistic, pragmalinguistic, sociopragmatic, strategic and discourse competences). Ninety-two 2nd year English major students, of similar proficiency levels, were assigned to either a control or experimental group for the period of the trial. The control group received input from two textbooks commonly used in Japanese universities, while the experimental group received input from authentic materials (films, documentaries, ‘reality shows’, TV comedies, web-based sources, home-produced video of native speakers, songs, novels and newspaper articles), designed to allow students to ‘notice’ features of the discourse which could help them develop some aspect of their communicative competence. The hypothesis was tested with a batch of eight pre/postcourse measures, designed to tap into different aspects of learners’ communicative competence or language skills: a) Listening; b) Pronunciation; c) ‘C’-Test; d) Grammar; e) Vocabulary; f) Discourse completion task (DCT); g) IELTS oral interview; h) Student-student role-play. These were supported with qualitative results from learners’ diaries, case-study interviews with subjects from both groups and transcripts of classroom interaction. Univariate analysis of the pre/post-course tests, using ANCOVA, indicated statistically significant differences between the two treatment groups, with the experimental group out-performing the control group in five of the eight communicative competence measures. The qualitative results of the trial helped to account for these differences in performance, suggesting that the authentic materials, and their associated tasks, allowed learners to notice a wider range of discourse features than those generally available in textbook input. They also indicated a clear preference in the experimental group for authentic materials over textbooks, suggesting that learners found them more interesting, varied and challenging, and better able to meet their perceived future language needs. Finally, the qualitative results demonstrated that, for learners, social goals often override instructional goals in the classroom, suggesting that classroom-based research benefits from both an emic and etic perspective in order to fully account for results.